POS1149 BONE MANIFESTATIONS IN SYSTEMIC MASTOCYTOSIS AND RELATED RISK FACTORS
Authors: H. Avalos Bogado, M. Barceló-Bru, M. Pascual-Pastor, A. D. Ulloa Navas
Journal: Annals of the Rheumatic Diseases (2022)

Background Clinical characteristics in Systemic Mastocytosis (SM) range from asymptomatic (indolent) to aggressive forms. Up to 28-34% of patients with SM have symptoms related to bone involvement at diagnosis and 16% have fractures (1). Skeletal manifestations include bone pain, osteoporosis (OP), osteosclerosis, focal osteolytic and osteoblastic lesions. OP is frequently related to indolent SM but not the aggressive forms (2). Objectives To describe bone involvement in patients with SM and analyze related risk factors. Methods Retrospective cohort study comprising patients with SM that attended the Rheumatology Department from 2010 to 2021. Sociodemographic variables, SM classification, OP risk factors, bone lesions, fracture presence and analytical parameters were collected, and we analyzed whether they were associated with the presence of fractures (Table 1). Densitometry data were registered at diagnosis and up to 8 years of follow-up. Table 1. Clinical features and differences between fractured and not fractured patients ALL Fractures No fractures p (N=22 ) (N=3 ) (N=19 ) Age (y), mean (SD) 47.05(12.4) 44.3 (13.3) 47.5 (2.5) 0.69 Sex W/M, N(%) 15(68.2)/7 (31.8) 1(33.3)/2(66.7) 14 (73.7)/5(26.3) 0.23 Mastocytosis classification N(%) 0.37 Indolent 19(86.4) 2(66.7) 17 (89.5) Aggressive forms * 3(13.6) 1(33.7) 2(10.5) Menopause, N(%) 8 (36.4) 1 (100%) 7(83.6) 0.66 Low calcium intake, N(%) 16(72.7) 2 (66.7%) 14 (73.7) 0.63 Low BMI, N(%) 5 (22.7)/17(77.3) 0 5(26.3) 0.44 Smoking, N(%) 2 (9.1) 0 2 (10.5) 0.74 Alcoholism, N(%) 2(9.1) 0 2 (10.5) 0.74 Hypovitaminosis D, N(%) 5(22.7) 0 5(41.7) - Hyperparathyroidism , N(%) 5(22.7) 0 5(45.5) - Tryptase, mean (SD) 34.4(26.1) 20(-) 35.3(26.7) 0.58 BMD at diagnosis, mean (SD) Lumbar spine (g/cm 2 ) 0.976 (0.2) 0.509 1.012(0.1) &lt;0.01 Femoral neck (g/cm 2 ) 0.860 (0.1) 0.704 0.872(0.1) 0.17 *Aggressive forms include smoldering, hematologic malignancy, and mast cell leukemia Results 22 patients were included, 19 SM were indolent, 1 smoldering, 1 hematologic malignancy and 1 mast cell leukemia. Radiologically, 17 patients did not present lesions, 4 presented sclerotic lesions and 1 lytic lesions. Vertebral fractures were observed in 3 patients and 2 of them were before SM diagnosis. 10 patients received anti-osteoporotic treatment, 3 of them with teriparatide. At diagnosis, 2 patients (9.1%) had osteoporosis and 11 (50%) osteopenia. None of the analyzed risk factors were associated with OP presence. Of note, during follow-up significant changes were observed between those with indolent SM and aggressive forms at lumbar spine (LS) and femoral neck (FN) at 2 years (change in LS in indolent form -2.9% vs 29.6% in aggressive forms, p &lt;0.001 and change at FN of 1% vs 20.5%, respectively, p=0.003). At 4 years change at LS was -4.1% vs 25.8%, p=0.034 between indolent and aggressive forms but there were no differences regarding the presence of fractures (2 fractures in indolent group and 1 in aggressive, p=0.371). Conclusion Bone involvement was present in more than 50% of patients at diagnosis and the presence of fractures was not uncommon (14%), especially at lumbar spine (LS). Aggressive forms were associated with an increase in aBMD. The presence of fractures was associated with lower LS aBMD at diagnosis. References [1]Carrasco Cubero C, Chamizo Carmona E. Reumatol Clin 2016; 107-109. [2]Gehlen M, Schmidt N, Pfeifer, M. et al. Calcif Tissue Int 2021; 109: 685-695. Disclosure of Interests None declared